Reactive extrusion runs a chemical reaction, such as grafting, coupling or chain modification, inside the extruder barrel while the polymer melt is being shaped, instead of shaping an already-finished resin. Standard extrusion is a purely physical forming step; reactive extrusion adds initiator chemistry, controlled residence time and often a degassing zone to remove reaction byproducts. Because the reaction and the shaping happen in the same equipment, screw configuration and residence time become patentable process variables in their own right, which is why they show up so heavily in this dataset's claims.

Filing in this space mixes established industrial polymer companies with university and research-institute co-filers, particularly a French academic-industrial cluster that appears repeatedly as co-assignee across multiple related filings. No single filer shows activity in the most recent tracked year, so today's leader by cumulative family count is not necessarily the most active filer going forward. A full assignee ranking, drawn from the underlying 147 families, is the more reliable way to identify current leaders than any single headline name.

The 2022 reading of zero sits at the midpoint of a trend that later peaked at 13 filings in 2024, which suggests the field grew through a late, concentrated burst rather than steady year-on-year increases. The apparent gap at 2026 is almost certainly a publication-lag artefact: patent applications typically publish around 18 months after filing, so recent-year filings are systematically undercounted in any dataset with a mid-2026 cut-off. Neither reading should be treated as evidence that interest in reactive extrusion has stopped.

Relative to the dense coverage of core shaping-of-plastics claims (B29C, 88 of 147 records), several adjacent branches show thinner filing: degassing-zone screw geometry tuned for volatile-heavy feedstocks, initiator selection specific to recycled or post-consumer polyolefin streams, in-line detection of gel formation during grafting, and residence-time control across multi-extruder reactive trains. Layered-product integration (B32B overlap) is also comparatively light at 9 records. These are candidate areas for a first-mover filing rather than crowded prior art.

Heavily-cited older patents remain important for freedom-to-operate precisely because citation counts accumulate over time and older records have had more years to be cited by everything that followed; US5367022A's 132 citations reflect decades of downstream grafting art building on it, not that it is currently the most commercially relevant filing. A sound FTO review still needs to check current filing activity and recent assignee behaviour alongside these foundational records, since the underlying claims may have expired or narrowed even as citation weight stays high.